Method and system for securing temperature sensors on the outer surface of a tank of an electric water heater

ABSTRACT

A temperature sensor securing system and method is described for securing two or more temperature sensors against an outer surface of a side wall of a tank of an electric water heater. The temperature sensors are secured spaced apart on an elongated support such as a circuit board which is held in position against the tank outer surface by support means. An expandable liquid foam causes the temperature sensors to be biased against the outer surface of the tank side wall to sense the temperature of the side wall at the location of the sensors and to generate actual temperature signals to a controller which is programmed to communicate with a subscriber and/or energy provider to control the water temperature inside the tank.

TECHNICAL FIELD

The present invention relates to a method and a system for securingtemperature sensors spaced apart vertically along the outer surface of atank of an electrical water heater to provided temperature signals tocontrol means to monitor the temperature of water within the tank andprovide adjustment of the water temperature.

BACKGROUND OF THE INVENTION

Reference is made to U.S. Pat. No. 10,101,216, issued to Applicant onOct. 16, 2018 and which relates to a metal conduit positioned verticallyagainst the tank wall of an electric water heater and in which isremovably positioned al elongated narrow circuit board on which aremounted temperature sensors to sense the temperature exposed to thetemperature sensors, herein thermistors. In one embodiment an elongatedvertical through is formed against the tank wall to permit thetemperature sensors to be positioned closely space to the tank wallwhile permitting the circuit board to be removed is any one of thetemperature sensors or the entire circuit board require replacement.

In recent years, and due to the increase cost of electricity, moresophisticated control systems have been developed to control theoperation of the water heater whereby to operate the resistive heatingelements during non-peak hours when electricity costs are lowest tocreate a reserve of hot water for use during peak-hours to reduce theoperating time of the elements when electricity is at a premium.Applicant has also disclosed in pending patent applications the need tocontrol the temperature of the water at the bottom end of electric waterheaters to a temperature sufficiently high to prevent the proliferationof bacteria and particularly the Legionella bacteria. It is known thatthis bacteria does not survive at temperatures in the range of 140degrees Fahrenheit. Therefore, it is of importance to monitor thetemperature in this area of the tank and to control the heating elementsin the tank to assure that such temperature be maintained in this bottomarea of the tank. There is also a need to monitor the temperatureprofile of the water within the tank of such water heater by the gridprovider.

Utilities also have a need to take control of water heaters to preventovercharging its grid during peak hours and to use its electricity whenthe demand is low as well as the cost. Such control would create anequilibrium or a mean demand of electricity from the grid. Stillfurther, after power outages when electricity is restored, it isdesirable for the utility to control the load to prevent an overload onthe grid. Control devices have been developed and continue to bedeveloped to remotely control the actuation of the resistive heatingelements of the water heaters at the customer locations while attemptingto satisfy the hot water demands of the customers. In order to achievethis, it is necessary to determine the temperature of the hot waterreserve inside the tank of the water heater. Accordingly, temperaturesensors are required to provide actual temperature values at distinctlocations of the water tank and particularly in the uppermost region ofthe tank where the hottest water is located and drawn. As abovementioned it is also important to monitor the temperature at the bottomend of the tank where bacteria can develop and propagate in the sedimentdeposits in the cavitated area surrounding the dome-shaped bottom wallof the tank.

Thermistors are excellent electrical components for sensing temperaturevariations as its resistance varies with temperature changes. Becausethe water tank is constructed of steel material which is a good thermalconductor, by sensing the temperature of the steel by mountingthermistors there against, the temperature of the water inside the tankcan be fairly accurately determined. To ensure a desired hot watervolume in the tank, it is necessary to monitor the temperature of thewater in the region of the heating elements. Because the thermistorsneed to be mounted outside the water tank wall, there is often no accessto these sensor components once the thermal insulation foam is injectedabout the tank wall sealing access to these devices and their wiring.Water heaters are now being manufactured with three resistive heatingelements to achieve better control of the water temperature in the tankand by selecting the operation of the various heating elements, some ofwhich may be of a much lower wattage than the others. Thus, threethermistors would be required to monitor the temperature of the tankwall in the region of the three resistive heating elements. Because ofthe insulation blown inside the gap formed between the outer skin of thewater heater and the water tank, there would be a need to form foam damsabout the thermistors and access doors in the outer casing for access tothe thermistors in case of a defect. This is not practical and adds tocost. Also, it complicates the troubleshooting and repair and does notremedy a defective wiring problems that could occur between thethermistors.

Mounting the thermistors on the tank wall and sealing them with the foaminsulation would require replacing the hot water heater to remedy adefective thermistor problem or a defective associated wiring probleminside the water heater.

It would be desirable to use the foam insulation of the tank to bias thetemperature sensors directly against the tank wall to achieve animproved temperature reading while surrounding the temperature sensorswith thermal insulation. It would also be desirable to permit the use ofthe expanding insulation to apply pressure against the temperaturesensors to assure good contact with the tank wall and also permittingthe circuit board to be removable for its replacement should there be adefect in the wiring or the temperature sensors.

SUMMARY OF THE INVENTION

It is therefore a feature of the present invention to provide atemperature sensor securing system and method which makes use of theexpansion of the thermal insulation disposed between the outer surfaceof the tank and the outer casing of the water heater to pressure biasthe temperature sensors against the outer surface of the tank of anelectric water heater.

Another feature of the present invention to position temperature sensorsalong a vertical orientation against the outer surface of a tank of anelectrical water heater to provide temperature readings from the bottomend of the tank to a top end where hot water is drawn from the tank.

Another feature of the present invention is to provide monitoring ofwater temperature in the bottom end of the tank of an electric waterheater whereby to control the temperature of water at the bottom end toprevent the development of bacterial and particularly the Legionellabacteria.

A still further feature of the present invention is to securetemperature sensors at predetermined positions on an inner surface of anexpandable foam pouch disposed in the insulation space between the tankouter surface and an outer casing of the water heater to automaticallysecure the temperature sensors against the tank outer surface when thefoam forming liquid within the pouch is expanded and to apply a pressureagainst the temperature sensors while surrounding the temperaturesensors with insulation and thereby obtaining a more precise reading ofthe temperature of the wall of the tank at the location of thetemperature sensor.

Another feature of the present invention is to use the expandable foamto apply pressure on a flexible conduit in which a circuit board onwhich is mounted temperature sensors to pressure bias the sensorsagainst the tank outer surface while permitting frictional slidingremoval of the circuit board.

According to the above features, from a broad aspect, the presentinvention provides a temperature sensor securing system for sensingwater temperature inside a water heater tank at predetermined levels.The system comprises an elongated support member on which is secured atleast two temperature sensors spaced-apart at predetermined positionsalong the support member. Biasing expandable foam retains the elongatedsupport member against an outer surface of a side wall of the tank andalong a longitudinal axis of the tank to position the at least twotemperature sensors in contact with the outer surface of the side wallto sense the temperature of the outer surface of the side wall at thepredetermined positions of the temperature sensors. The temperaturesensors are secured to conductors for connection to a signal processorprogrammed to generate data representative of the temperature sensed bythe at least two temperature sensors and wherein the sensed temperaturehas a correlation to the actual temperature of water inside the tank inthe area of the predetermined position of the temperature sensors.

According to another broad aspect of the present invention there isfurther provided a temperature sensor securing system for sensing watertemperature inside a water tank of an electric water heater atpredetermined levels. The temperature sensor securing system comprisesan expandable foam pouch of flexible material dimensioned for insertionbetween an outer surface of the water tank and an outer casing of thewater heater surrounding the outer surface of the water tank spaced apredetermined distance from the outer surface to form a surroundinginsulation space. The expandable foam pouch has an inner flexible sheeton an outer surface of which is attached at least two temperaturesensors at different spaced-apart locations wherein when a foam formingliquid is inserted into the expandable foam pouch, the pouch is causesto expand and deploy into the insulation space. The at least twotemperature sensors become pressure biased against the outer surface ofthe tank at east two different spaced apart locations by the expandablefoam pouch to sense the temperature of the outer surface of the tankrepresentative of the water temperature in the tank at the at least twodifferent spaced locations.

According to a still further broad aspect of the present invention thereis provided a method for securing at least two temperature sensorsagainst an outer surface of a tank of an electric water theater. Themethod comprises the following steps. (i) Providing an elongated circuitboard on which is mounted the at least two sensors at predeterminedspaced intervals to sense the temperature of the outer surface of thetank at the predetermined spaced intervals. The sensed temperature has acorrelation to the actual temperature of water in the tank at the spacedintervals. (ii) Retaining the at least two sensors against the outersurface of the tank along a longitudinal axis of the tank, and (iii)pressure biasing the at least two sensors against the outer surface ofthe tank by means of an expandable foam acting the temperature sensors.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will now be describedwith reference to the accompanying drawings which are representative ofexamples of the preferred embodiments and wherein;

FIG. 1 is a simplified fragmented side view of an electric water heaterillustrating the tank on which is secured the temperature sensors andwherein the tank is surrounded by an expandable foam materials disposedbetween the tank outer surface and the outer casing of the tank;

FIG. 2 is a fragmented cross-sectional view illustrating the securingsystem of the temperature sensors mounted inside an elongated channeland in which is injected an expandable foam the retain the temperaturesensors against the tank outer side wall in a thermal insulating manner;

FIG. 3 is an enlarged cross-sectional view of a modified version of FIG.2 and wherein the temperature sensors are mounted on a circuit boardwhich is disposed in a flexible channel retained against the outersurface of the tank wall and wherein the expandable foam of theinsulation pressure biases the temperature sensors against the outersurface of the tank wall with the circuit board being removable from thechannel form a top end of the channel with the temperature sensors infrictional sliding movement on the outer surface of the tank wall;

FIG. 4 is a cross-section view illustrating the flexible channel securedto the outer surface of the tank wall by an adhesive tape with theexpandable foam acting directly on the flexible channel;

FIG. 5 is a fragmented side view of a flexible material pouch on whichtemperature sensors are attached and wherein the pouch has sealedopenings through which the wires of the temperature sensors are madeavailable for connection to a controller, and

FIG. 6 is a simplified block diagram illustrating a controller systemconnected to the temperature sensors for monitoring the internal watertemperature of the tank and controlling the operation of electricheating elements within the tank to control the internal watertemperature to ensure sufficient hot water supply and prevent bacteriaproliferation at the bottom end of the tank.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to the drawings, and more particularly to FIGS. 1 to 4,there is shown a tank 10 of an electrical water heater 11 encased withina thermal insulating jacket 12 constituted by expandable foam material13 deployed within an insulating space 14 defined between the outersurface 15 of the tank 10 and an outer surrounding casing 16 of thewater heater. The tank 10 rests on a rigid insulating foam base 17disposed at a bottom end of the tank and a further rigid insulating foamcap 18 is secured to the top end of the tank. Accordingly, the tank 10is completely surrounded by thermal insulation.

An elongated channel member 19 is retained on the outer surface 15 ofthe tank 10 before the installation of the outer casing 16 and isretained along a substantially long axis of the tank by clamps 20 oradhesive tapes 21. As shown, the clamps 20 have a leaf spring 20′ shapedto engage the elongated channel member 19 and apply pressure thereagainst to immovably retain the channel member 19 along a straightvertical axis on the outer surface 15 of the tank side wall 15′. Theelongated channel member 19 as herein illustrated defines a generallyU-shaped wall 25 with a longitudinal side opening which is held againstthe outer surface 15 of the tank side wall 15′. An elongated straightflat and narrow circuit board 22, on which at least two temperaturesensors 23 are secured at predetermined spacing, is positioned withinthe elongated channel member 16 with the temperature sensors facing andin contact with the outer surface 15 of the tank side wall 15′.

Biasing means, in the form of an expandable foam material 24, isinjected into the space between the circuit board 22 and the innersurface 19′ of the channel member 19 from a top end of the channelmember whereby to exert pressure on the back side of the circuit boardand firmly bias the temperature sensors against the outer surface 15 ofthe tank side wall 15′. The temperature sensors generate temperaturevalue signals representative of the temperature of the tank wall surfaceat the predetermined locations of the temperature sensors. Thetemperature value signals are representative of the water temperatureinside the tank at the predetermined locations of the temperaturesensors 23. The temperature of the tank side wall at the differentlocations corresponds substantially to the water temperature inside thetank adjacent the temperature sensors or is correlated thereto. It ispointed out that three or four or more temperature sensors 23 may besecured to the circuit board 22 and positioned against the outer surfaceof the tank side wall from a bottom end 26 of the tank to a top position27 where hot water is drawn out of the tank 10.

With reference to FIGS. 3 and 4, there is shown a modification of theFIG. 2 embodiment, and wherein a thin and shallow U-shaped non-metallicbarrier strip 30 of flexible material is attached to the tank side wallouter surface 15 by adhesive tapes 31 whereby to permit the circuitboard 22 and the temperature sensors secured thereto to be removablysecured within the channel member 19 by frictional sliding contact ofthe temperature sensors 23 with the tank side wall. The barrier strip 30has a flat channel cross-section defining opposed side spacer feet 32which rests on the outer surface of the tank side wall to prevent foammaterial from entering the space 33 wherein the circuit board isdisposed. Because the barrier strip 30 is constructed of thin flexiblematerial, such as plastics, it can flex under the influence of expandingfoam material to apply and maintain sufficient pressure against thecircuit board to retain the circuit board at the desired position insidethe barrier strip 30 and bias the temperature sensors 23 against thetank outer surface. For such a removable design to be functional, thechannel member 19 would extend to an uppermost position of the tank sidewall 15 as shown by dotted lines 19″ in FIG. 1 and terminate just underthe foam cap 18.

As shown in FIG. 4, a further embodiment, the barrier strip 30 need notbe located within the elongated channel member 19 and can be exposed tothe insulation space 14. Accordingly, when the foam material 13 isexpanded within the space 14 pressure is applied against the barrierstrip side wall 30′ and exerts a biasing force against the temperaturesensors 23 to place them in pressure contact against the outer surface15 of the tank side wall 15′.

With reference now to FIG. 5 there is shown another embodiment ofsecuring the temperature sensors 23 against the tank outer surface 15.As herein illustrated, the temperature sensors 23 are secured to anexpandable foam pouch 35 constructed of flexible plastic film materialand dimensioned for insertion into the insulation space 14 between theouter surface 15 of the tank side wall 15′ and the inner surface 16′ ofthe outer casing 16. As herein shown, temperature sensors 23 are mountedon an elongated flexible support strip 37 which is attached to the innerflexible wall 36 of the pouch 35 along a straight vertical position. Thesupport 37 may be glued or taped onto the pouch inner surface 36. Thetemperature sensors 23 are secured in a spaced-apart predeterminedposition to sense the temperature of the tank outer surface at specificlocations to generate temperature signals at such locations. As hereinshown, sealed access openings 39 are formed in the expandable foam pouch35 between the inner flexible sheet 36 an outer flexible sheet 40thereof. These openings are precisely located on the pouch to line-upwith the resistive heating element connectors of the tank, herein twosuch resistive heating elements 45 as shown in FIG. 6. The signalcarrying wires 41 connected to the temperature sensors are positioned inone of these access openings for connection to a controller as furtherdescribed herein below.

In order to secure the temperature sensors 23 against the thank sidewall 15′, the foam pouch is inserted into the insulation space 14 withthe lower edge 38 of the foam pouch disposed toward the bottom of theinsulation space 14 and surrounding the tank. The pouch is furtherprovided with holes 42 to permit insertion of an expandable foamingliquid, herein urethane which when expanding into foam causes the pouchto expand and deploy into the insulation space 14 causing the supportstrip 37 to position itself against the tank wall with the temperaturesensors 23 biased against the outer surface 15 of the tank side wall 15′substantially at the predetermined locations. One of the openings 42 isprovided to cause excess expanding foam to exit the pouch after theentire space 14 as been filled with the expanded foam pouch.

With reference now to FIG. 6, the conductors or wires 41 of thetemperature sensors 23 of tall of the embodiments described herein, feedcontinuous actual temperature signals to a processor 51 of a controllercomputer 50 which has a memory 52 which is programmed to store data andtransmit data to various control devices, such as a subscriber controldevice 53 to permit the subscriber to input commands to the computer 50to effect certain stored functions such as the control of the resistiveheating elements 45 to control the water temperature in the tank 10. Thecontroller is programmed to monitor water temperature throughout thetank and to maintain a desirable programmed temperature.

As further illustrated in FIG. 6, the controller is made accessible to aremote energy provider 55 through a communication link, such as aninternet link 56, to have access to the data relating to the temperatureof the water within the tank 10 of the electric water heater of thesubscriber to permit the energy provider 55 to control the operation ofthe resistive heating elements 45 to maintain desired temperature of thewater within the tank 10. For example, and has described in co-pendingpatent applications of the Applicant, it is important to maintain awater temperature at the bottom of the tank, near the dome-shaped bottomwall 58 of the tank, in the range of about 140 degrees Fahrenheit inorder to prevent bacteria proliferation. In an event where there is apower failure on the grid 57 for a long period of time, the subscribersneed to have their water heaters controlled by the provider not tooverload the grid when power restored. The controller 50 permits theprovider to have access to water temperature at different levels insidethe tank 10 and to operate individual ones of the resistive heatingelements to start heating water more slowly to control the overalldemand from the grid.

The present invention thus provides a method for securing at least twotemperature sensors 23 against an outer surface 15 of a tank side wall15′ of an electric water theater. The method can be summarized by thesteps of providing an elongated circuit board 22 on which is mounted atleast two sensors 23 at predetermined spaced intervals to sense thetemperature of the outer surface 15 of the tank side wall 15′ atpredetermined spaced intervals. The sensed temperature signals have acorrelation to the actual temperature of water in the tank 10 at thespaced intervals. The least two sensors 23 are retained against theouter surface of the side wall of the tank along a longitudinal axis oftank, and the temperature sensors 23 are pressure biased against theouter surface of the tank by means of an expandable foam acting thereagainst.

The method further provides the steps of attaching an elongated u-shapedchannel member 19 against the outer surface 15 of the side wall 15′ ofthe tank 10 along the longitudinal axis with an elongated opening of thechannel facing the outer surface of the tank. The elongated circuitboard 22 is positioned inside the channel member 19 from a top end ofsaid channel member with the temperature sensors facing the outersurface of said tank. A foam forming liquid is injected between thecircuit board 22 and an inner surface 19′ of said u-shaped channelmember 19 wherein upon expansion of the foam the at least two sensors 23are pressure biased against the outer surface 15 of the side wall 15′ ofthe tank 10. A barrier strip 30 may be mounted between a rear surface ofthe circuit board 22 before injecting the foam forming liquid to providefrictional sliding contact of the circuit board therewith to permitremoval and replacement of the circuit board if there is a defect in thewiring of the temperature sensors.

In another embodiment the method provides for the attachment of anelongated support 37 to an inner flexible sheet 36 of an expandable foampouch 35 of flexible material. The expandable foam pouch 35 is disposedin the surrounding insulating space 14 formed between said outer surface25 of said tank and an outer casing 16 of the water heater and which issecured in a spaced-apart manner about the tank 10. A foam formingliquid is injected into the expandable foam pouch 35 to cause the pouchto expand and deploy into the insulation space 14 to cause the at leasttwo temperature sensors 23 to be pressure biased against the outersurface 15 of the side wall 15′ of the tank along a substantiallylongitudinal axis.

It is within the ambit of the present invention to cover any obviousmodifications of the examples of the embodiment described hereinprovided such modifications fall within the scope of the appendedclaims.

1. A method for securing at least two temperature sensors against anouter surface of a tank of an electric water theater, said methodcomprising the steps of: i) providing an elongated circuit board onwhich is mounted said at least two sensors at predetermined spacedintervals to sense the temperature of said outer surface of said tank atsaid predetermined spaced intervals, said sensed temperature having acorrelation to the actual temperature of water in said tank at saidspaced intervals, ii) retaining said at least two sensors against saidouter surface of said tank along a longitudinal axis of said tank, andiii) pressure biasing said at least two sensors against said outersurface of said tank by means of an expandable foam acting thereagainst.
 2. The method as claimed in claim 1 wherein there is furtherprovided the steps of attaching an elongated u-shaped channel memberagainst said outer surface of said tank along said longitudinal axiswith an elongated opening of said channel facing said outer surface ofsaid tank, positioning said elongated circuit board in said channelmember from a top end of said channel member with said temperaturesensors facing said outer surface of said tank, and injecting a foamforming liquid between said circuit board and an inner surface of saidu-shaped channel member wherein upon expansion of said foam said atleast two sensors are pressure biased against said outer surface of saidtank.
 3. The method as claimed in claim 2 wherein said step of attachingsaid elongated u-shaped channel member is effected by one of clampingsaid u-shaped channel member against said outer surface of said tank andattaching said u-shaped channel member by adhesive tapes, and whereinthere is further provided the step of positioning a barrier stripbetween a rear surface of said circuit board before said step ofinjecting said foam forming liquid, said barrier strip providingfrictional sliding contact with said circuit board to permit removal andreplacement of said circuit board.
 4. The method as claimed in claim 1wherein after said step (i) there is provided the steps of attachingsaid elongated circuit board to an inner flexible sheet of an expandablefoam pouch of flexible material, inserting said expandable foam pouch ina surrounding insulating space formed between said outer surface of saidtank and an outer casing of said water heater secured in a spaced-apartmanner about said tank, and injecting a foam forming liquid into saidexpandable foam pouch to cause said pouch to expand and deploy into saidinsulation space to cause said at least two sensors to be pressurebiased against said outer surface of said tank along said longitudinalaxis.
 5. The method as claimed in claim 1 wherein there are at leasthree of said sensors to provide temperature value signalsrepresentative of water temperature from a bottom end of said tank to atop end position where hot water is drawn out of said tank, conductorssecured to said temperature sensors and to a controller having aprocessor equipped with a memory in which is stored functions forexecution by a computer of said controller, said sensors generatingcontinuous temperature value signals to said controller, said controllercommunicating with a utility provider capable of instructing saidcontroller to effect selected functions stored in said memory andcapable of controlling power supplied to resistive heating elements ofsaid electric water heater, said functions including without limitationsone of or a combination of (a) shedding surplus power from a power gridof said utility, (b) controlling power consumption of said electricwater heater, (c) operating a switch mounted with said water heater tocut power supplied to said electric water heater resistive heatingelements and to return power thereto, and (d) maintaining a desiredtemperature at said bottom end of said tank to prevent harmful bacteriaproliferation.